Impact of thermal energy storage system on the Solar Aided Power Generation plant with diverse structure and extraction steam operation strategy

Solar Aided Power Generation (SAPG) plant is a type of solar thermal hybrid system. In such a system, the coupling of solar field and regenerative Rankine cycle plant is achieved through a heat exchanger system used to facilitate heat exchange process between solar fluid and feedwater to boiler. The extraction steam, which is used to preheat feedwater, is replaced/adjusted and expended further in the steam turbine to generate power. The performance of such a hybrid power system is dependent on the combinations of heat exchanger configuration and extraction steam operation strategy. The present work optimises the combinations for the SAPG plant with diverse thermal energy storage (TES) capacity, and evaluates the impact of thermal energy storage (TES) system on the SAPG plant with different combinations. A 300 MW SAPG plant is used as case study. The results indicate that the optimal combinations are heat exchanger being arranged in rear series of or in parallel of the replaced feedwater heater and replacement order of extraction steam being from high to low grade stages. The technical performance of optimal combinations are about 1.15 % to 8.85 % higher than the most commonly evaluated combinations for the SAPG plant without TES system. TES system would reduce the advantages of the optimal combinations over other combinations. However, this negative effect is very small and can be ignored. The integration of the TES system would increase the LCOE for all combinations. This impact of the TES system on the LCOE decreases with the increase in SM value.